Safety device for hot-air furnaces



Oct. 16, 1928. 7 1,688,121

J. M. LA RSON SAFETY DEVICE FOR HOT AIR FURNACES Filed June 9, 1926diggi- Patented Oct. 16, 1928.

UNITED STA TES PATENT OFFICE.

JOHN M. LARSON, OF CHICAGO, ILLINOIS, ASSIGNOR 'IO' NATIONAL REGULATORCOM- rm, or on'rcaco, ILLINOIS,

A CORPORATION O F'ILLINOIS.

SAFETY. DEVICE FOR HOT-AIR FURNACES.

Application filed June 9,

My invention relates to hot air furnaces and particularly to a safetydevice for automatically closing the draft door and opening the checkdoor when the furnace becomes overheated.

A11 object of my invention is to provide a device which may be installedin one of the ducts of a hot air furnace and which will be soconstructed that it will fuse at a predetermined temperature and thuscheck the combustion in the furnace so as to produce a damping actionand consequent reduction in temperature.

Another object of my invention is to provide a safety device which maybe used in combination with the regulating device shown in my Patent No.1,593,581, dated July 27 1926, and when used in connection therewith myimproved safety device will.

prevent any overheating of the furnace caused by the chains in saiddevice running ofl the pulleys or any other accident which may occur tothe parts of the said regulating device.

Other objects and advantages will be readily appreciated as the samebecome better understood by reference to the description when consideredin connection with the accompanying drawing, in which- Figure 1 is aside view of an ordinary hot air furnace showing my improved safetydevice applied thereto;

Fig. 2 is a like View showing the safety device applied in combinationwith the regulator shown and described in the above-mentionedapplication 5 Fig. 3 is a side view of the fusible member;

Fig. 4 is a front view of the same; and

Fig. 5 is a cross-sectional view of the warm air duct taken on the line55 ofFig. 1.

Like symbols of reference herein indicate like parts in each of thefigures of the draw- 11w.

Tteferring to the drawings in detail and first to Fig. 2, theconstruction shown comprises a hot air furnace which is of any usual orsuitable construction which has a ot air chamber, from the upper end ofwhich the usual pipe connections 7 lead. Thisfurnace, as shown, isprovided with a draft regulating door 8' and a draft check door 9'.- Thedoor 8, which is located at a osition near the bottom of the furnace,admits air'for the purpose of combustion and the door 9 provides a meansfor checking the draft and eachof 1926. Serial No. 114,606.

these doors is regulated by the temperature control regulator 11 shownin Fig. 2. For the details of operation of this regulator, at-

tention is called to the above-mentioned pat and from thence over apulley 17 (later described) the member 14 being connected at its lowerend to the draft door 8". The arm 13 of the regulator hasa flexible pullmember 18 passing over a sheave 19 secured in the same manner as thesheave 16, over a pulley 21 (later described), and over a sheave 22 themember 18 being connected to the check door 9. The flexible pull members14 and 18 are provided with counterweights 24 and 26 for assisting inbalancing the weights of their respective doors when the same are beingopened. The automatic regulator 11 is so constructed that on a rise oftemperature the arm 12 rises and the arm 13 is depressed. This tends toclose the draft door 8 and if the movement is continued sufficiently itopens the check door 9', thus checking the fire and tending to lower thefurnace temperature. After the temperature drops the arm 12 isloweredand the arm 13 is raised and this permits the closing of thecheck door 9 and the opening of the draft door 8, tending to increasethe heated effect. 1

In the device shown in Fig. 1, wherein the draft door is controlled bymeans of a flexible pull member 27, extending into the upper floor ofthe building through the flooring 28, the said flexible member passesaround the sheave 29 over a pulley 31 (later described) and is connectedto the draft door in like manner. The flexible pull member is providedwith a suitable counterweight 32 and at ashort distance above the samethe flexible pull member 33 is connected thereto, passes through an eyebolt 34 over a sheave 36 and is connected to the check door 9. If theroom becomes too warm the occupant Wlll lower the pull member 27permitting the draft door My improved safety device which is in tendedto prevent any overheating of the furnace and, consequently, the pipeconnections or ducts 7, in its preferred form, consists of a pair ofstrips of metal 37 and 38 which are overlapped and connected together bysolder or some fusible metal 39 which fuses at a low temperature, andsaid jointed strip extends entirely through the center of one of thewarm air ducts, as shown in Fig. 5. The lower end of the strip 38 isprovided with a series of holes 41 through which may be placed a ring42, a cotter pin, a bolt or any other suitable limiting member and theupper end of the strip 37, when used in connection with the device shownin Fig. 1, is provided with a flexible pull member 43-which passesthrough the eye bolts 44 and 46 and supports the pulley 31 over whichthe flexible pull member 27 passes.

This safety device and regulator are usually placed in the hot air ductleading to the living room or some room where the warm air is alwaysturned on, so that any overheating of the furnace will be immediatelychecked, which would not always be the case if the device were includedin some duct only used at intervals.

In the operation of the device shown in Fig. 1, it will be apparent thatwhen the temperature in the warm air duct rises to a degree sufficientto soften the solder or fusing metal 39, the upper strip 37 will bepulled upward through the opening in the duct. The flexible pull member43 will be drawn upward and around through the eyebolts 44 and 46 sothat the pulley 31 will be lowered and as the flexible pull member 27tends to straighten out with the assistance of the counterweight 32, thedraft door 8 will be closed and the flexible pull member 27 will bedrawn outward through the eyebolt 34 and over the sheave 36 in order toopen the check door 9. This will produce a dampened action on thecombustible material in the furnace and have a tendency to decrease thetemperature in the hot air duct.

In the construction shown in Fig. 2 where the safety device is used incombination with the regulator 11, the strip 37 has connected to itsupper end a flexible pull member 47 which passes through the eyebolts 48and 49 and supports the pulley 17 through which the flexible pull member14 extends, while the flexible pull member 51 also connects with theupper end of the strip 37, passes through the eyebolt 52, the eyebolt 53and supports the pulley 21 over which the flexible pull member 18extends. 1

When the safety device is used in connection with this regulatingmechani sm, and the joint 39 between the same is fused it permits ofupward movement of the strip 37 and the pulley 17 will be permitted todrop by the upward movement of the flexible member 47 through theeyebolts 48 and 49 so that the draft door 8 will be closed, while theflexible pull member 51,passing through the eyebolts 52 and 53 willpermit the pulley 21 to be lowered by the counter-weight 54 so that thecheck door 9' will be opened.

It will be apparent that, when the furnace has been damped by theoperation of the safety device and it is desired to again place the samein operative condition, the strips 37 and 38 can readily be reunited byholding a match or other heat-producing element to the fusible materialat the point 39 whereupon they may' be passed through the warm air ductand connected in the manner originally described; The gauge hole 56 willindicate the point for re-fusing the strips so that when they are againpassed through the duct all the connecting parts will be properly gaugedand in their original positions. Ordinarily, no additional fusingmaterial is required as all of the same is retained on the strips at thetime of their separation because of the fact that the fusing element 39does not melt but merely softens to permit the strips 37 and 38 toseparate.

It will also be understood that I do not limitmyself to strips of thedesign shown herein and it should be understood that the details ofconstruction are capable of wide modification and variation withoutdeparting from the spirit of the invention or sacrificing any of itsadvantages. Hence, I reserve all such variations, modifications andmechanical equivalents as fall within the spirit and scope of theappended claims.

I claim:

1. The-combination with a hot air furnace having heat controlling meansand a hot air pipe leading from said furnace for supplyin g hot air to aroom, of means for controlling said heat controlling means to preventexcessive rise of temperature, comprising a pair of strips havingoverlapping ends secured together by fusible material, said strips whenthus secured together forming a bar extending through said hot air pipe,with the overlapping ends located -in said hot air pipe, means forpreventing withdrawal of said bar from said hot air pipe so long 'as thetwo strips are connected together but permitting the withdrawal of bothstrips when the fusible material fuses, and connections betweenone ofsaid strips and said heat controlling 2. The combination with a furnacehaving a heat controlling door having a tendency to close, of means forcontrolling the positioning of said door, comprising a flexible memherand a pulley over which said flexible member passes, and heat releasedmeans for holding said pulley in position whereby when the temperaturebecomes excessive said pulley will be released from its operativeposition and the door will be closed.

3. The combination with a furnace having heat controlling means, oftemperature controlled means for movin said heat controllin means tovarious a justed positions to maintain an even temperature, andadditional temperature controlled means acting on said same heatcontrolling means to cause said heat controlling means to move to lowtemperature position upon an excessive rise of temperaturenotwithstanding the action of said first heat controlled means.

4. The combination with a furnace having heat controllin means, oftemperature controlled means or moving said'heat controlling means tovarious adjusted positions to maintain an even temperature, andadditional temperature controlled means acting. on'said same heatcontrolling means to cause said heat controlling means to move to lowtem- 20 perature position upon an excessive rise of tem eraturenotwithstanding the action of sai first heat controlled means, saidadditional temperature controlled means comprising meansforrendering-said first temperature controlled means ineffective to controlsaid heat controlling means.

5. The combination with a furnace having a heat controllin door having atendenc to close, of means 5n controllin the positioning of said doorcomprising a exible member and a pulley over which said flexible memberpasses, and heat released means for moving said door from closed to openposition comprising a weight connected with said flexible member andreleased when the temperature becomes excessive whereby it acts on saiddoor through said flexible member to open it.

In witness whereof, I have hereunto subscribed my name.

JOHN M. LARSON.

